Remote copy method and remote copy system

ABSTRACT

In a configuration in which it is necessary to transfer data from a first storage system to a third storage system through a storage system between the storage systems, there is a problem that it is inevitable to give an excess logical volume to a second storage system between the storage systems. A remote copy system includes first storage system that sends and receives data to and from an information processing apparatus, a second storage system, and a third storage system. The second storage system virtually has a second storage area in which the data should be written and has a third storage area in which the data written in the second storage area and update information concerning the data are written. Data sent from the first storage system is not written in the second storage area but is written in the third storage area as data and update information. The data and the update information written in the third storage area are read out from the third storage system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application relates to and claims priority from Japanese PatentApplication No. 2004-122431, filed on Apr. 19, 2004, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a storage system, and in particular tocopying of data among plural storage systems.

2. Description of the Related Art

In recent years, a technique has grown in importance in which, in orderto allow a data processing system to provide services even if a failurehas occurred in a storage system used for providing continuous servicesto customers (hereinafter referred to as first storage system), otherstorage systems (a storage system a relatively short distance apart fromthe first storage system is referred to as a second storage system, anda storage system a longer distance apart from the second storage systemis referred to as a third storage system) are set separately from thefirst storage system, and copies of data in the first storage system arestored in the other storage systems. As a technique for copyinginformation stored in the first storage system to the second and thethird storage systems, there are techniques disclosed in U.S. Pat. No.6,209,002 and JP-A-2003-122509.

U.S. Pat. No. 6,209,002 discloses a technique in which the secondstorage system has two copied data corresponding to copy object data inthe first storage system, and the third storage system holds one of thecopied data.

JP-A-2003-122509 discloses a technique in which the second storagesystem has only one copied data corresponding to copy object data in thefirst storage system, and the third storage system can obtain the copieddata without requiring a redundant logical volume for carrying outremote copy as described in U.S. Pat. No. 6,209,002.

As described above, in the conventional techniques, the second storagesystem is provided between the first storage system and the thirdstorage system, which is located a long distance apart from the firststorage system, to realize long-distance remote copy while preventingdata loss such that a copy of data in the first storage system isobtained in the third storage system.

However, some users may require a remote copy system in which cost forsystem operation is considered while failure resistance of data isincreased through long-distance copying. For example, a copy of data inthe first storage system only has to be held in a storage system locateda long distance apart from the first storage system.

In order to give a complete copy of data in the first storage system tothe third storage system, which is located a long distance apart fromthe first storage system, in preparation for a failure, when influenceon performance of the first storage system is taken into account, it isnecessary to arrange the second storage system between the first storagesystem and the third storage system and transfer the data from the firststorage system to the third storage system through this second storagesystem. In such a case, it is desired to minimize a logical volume thatis used in the second storage system as much as possible.

However, in the case in which it is attempted to remotely copy data fromthe second storage system to the third storage system located a longdistance apart from the second storage system, the second storage systemis required to have a volume (copied volume) that is the same as avolume of the first storage system. This volume increases as a capacityof the volume of the first storage system increases.

It is needless to mention that, even if the technique disclosed inJP-A-2003-122509 is applied, the second storage system inevitably hasthe volume with the same capacity as copy object volume in the firststorage system.

SUMMARY OF THE INVENTION

The present invention has been devised in view of such problems, and itis an object of the present invention to minimize or eliminate use of avolume in a second storage system for copying data when the data iscopied from a first site to a third site. In addition, it is anotherobject of the present invention to increase availability of a volumesuch that plural host apparatuses can set an area of the volume as anobject of writing.

In order to attain the above-mentioned objects, a form of the presentinvention has a constitution described below.

A remote copy system includes: a first storage system that sends andreceives data to and from a first information processing apparatus; asecond storage system that is connected to a second informationprocessing apparatus and the first storage system and receives data fromthe first storage system; and a third storage system that is connectedto the second storage system and receives data from the second storagesystem. In the remote copy system, the first storage system has a firststorage area in which data from an information processing apparatus iswritten, the second storage system has a logical address for storing acopy of the data but does not have an allocated storage area, and has asecond storage area in which the data and update information thereof arewritten, the data sent from the first storage system is written in thesecond storage area as the data and the update information, the thirdstorage system has a third storage area in which data read out from thesecond storage area in the second storage system and update informationconcerning the data are stored, and the data and the update informationstored in the second storage area are readout from the third storagesystem. The second storage system has a logical address for storing acopy of the data but does not have an allocated storage area, and thestorage area has a structure that can be used for transmission andreception of data to and from a second information processing apparatus.

According to the present invention, a copy object data can be copied tothe third storage system without requiring the second storage system tohave a complete copy of the copy object data in the first storagesystem. Consequently, a volume capacity in the second storage system canbe reduced. In addition, an actual volume, which is not required to beassigned, can be used for another application. Further, a specific areaof a volume can be used by plural host apparatuses. The host apparatusin this context means an information processing apparatus that issuesinstructions for writing data in and reading data from the specific areaof the volume. When writing of data in the volume of the second storagesystem is executed by a writing command issued from the first storagesystem, the first storage system is a host apparatus for the secondstorage system. It is needless to mention that an information processingapparatus such as a server can be a host apparatus for a storage system.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram showing a first embodiment of the presentinvention;

FIG. 2 is a block diagram showing an internal structure of a storagesystem;

FIG. 3 is a diagram showing a volume information table;

FIG. 4 is a diagram for explaining a journal;

FIG. 5 is a flowchart showing initial copy processing;

FIG. 6 is a diagram showing pair setting information;

FIG. 7 is a diagram showing a journal group setting information table;

FIG. 8 is a block diagram showing a flow of access instruction receptionprocessing;

FIG. 9 is a flowchart explaining the access instruction receptionprocessing;

FIG. 10 is a block diagram showing an operation (journal read receptionprocessing) of a channel adapter 50 of a storage system 15 that hasreceived a journal read instruction;

FIG. 11 is a flowchart explaining journal read instruction receptionprocessing;

FIG. 12 is a block diagram showing restore processing;

FIG. 13 is a flowchart showing the restore processing;

FIG. 14 is a block diagram showing a second embodiment of the presentinvention;

FIG. 15 is a flowchart showing initial setting processing in the secondembodiment;

FIG. 16 is a diagram showing pair setting information;

FIG. 17 is a block diagram showing a flow of access instructionreception processing in the second embodiment;

FIG. 18 is a flowchart showing the access instruction receptionprocessing in the second embodiment;

FIG. 19 is a block diagram showing a third embodiment of the presentinvention;

FIG. 20 is a diagram showing a connection information table;

FIG. 21 is a diagram showing an example of a setting screen for pairgeneration that is displayed on a host computer or a maintenanceterminal in a fourth embodiment of the present invention;

FIG. 22 is a block diagram showing a case in which a job is taken overby a third site when a failure has occurred in a first site; and

FIG. 23 is a block diagram showing a case in which a job is taken overby a second site when a failure has occurred in the first site.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be hereinafter described withreference to the accompanying drawings.

First Embodiment

FIG. 1 is a block diagram showing a first embodiment of the presentinvention. FIG. 1 shows an entire remote copy system including pluralstorage systems. A storage system 10 is connected to a host computer 5via a connection line 210. (According to circumstances, this storagesystem 10 will be hereinafter referred to as a first storage system, anda data processing system including this first storage system and thehost computer 5 will be hereinafter referred to as a first site.)

A storage system 15 is connected to the first storage system 10 via aconnection line 220. (According to circumstances, this storage system 15will be hereinafter referred to as a second storage system, and a dataprocessing system including at least this second storage system will behereinafter referred to as a second site or an intermediate site.)

A storage system 20 is connected to the storage system 15 serving as thesecond storage system via a connection line 240. (According tocircumstances, this storage system 20 will be hereinafter referred to asa third storage system, and a data processing system including at leastthis third storage system 20 will be hereinafter referred to as a thirdsite.)

The connection lines 210, 220, and 240 may be directly connected linessuch as fiber cables or may be connection via a wide-area network suchas the Internet.

The storage system 10 in the first site retains a logical volume 110(ORG1) and a logical volume 120 (ORG2). In this embodiment, it isassumed that an original data to be a copy object is stored in thelogical volume 110 (ORG1).

The storage system 15 in the second site retains a copy of the logicalvolume 110 (ORG1) as a logical volume 150 (Data 1). The storage system20 in the third site retains a logical volume 200 (Data 2) in whichcopied data is stored.

Here, a capacity and a physical storage position (physical address) of alogical volume, which are defined in the storage systems 10, 15, and 20,can be designated using maintenance terminals (not shown) such ascomputers connected to the respective storage systems or host computers5, 6, and 7, respectively.

In the following description, in order to facilitate distinction betweencopy object data and copied data, a logical volume, in which the copyobject data is accumulated, will be referred to as a primary logicalvolume, and a logical volume, in which the copied data is accumulated,will be referred to as a secondary logical volume. The primary logicalvolume and the secondary logical volume forming a pair will be referredto as a pair. A relation between the primary logical volume and thesecondary logical volume, states of the primary logical volume and thesecondary logical volume, and the like are saved as a pair settinginformation table 500 in shared memories (SMs) 70 in the respectivestorage systems to be described later.

First, an example of a hardware configuration of the storage system 10shown in FIG. 1 will be described with reference to FIG. 2. The secondstorage system, which is shown as the storage system 15 in FIG. 1, issimply illustrated as the second storage system 15 in FIG. 2.

The first storage system 10 has plural channel adapters 50 forconnecting the first storage system 10 to the host computer 5. Thesechannel adapters 50 are connected to the host computer 5 and the secondstorage system 15 via the connection line 210.

The channel adapters 50 are connected to caches 60 via a connection unit55, analyzes a command received from a host apparatus, and controlsreading-out and writing of data, which is desired by the host computer5, on the caches 60. The logical volume 110 (ORG1) and the logicalvolume 120 (ORG2) are arranged over plural HDDs 100.

FIG. 3 shows an example of a table in which logical volumes and physicaladdresses on the HDDs 100 are defined, and capacities, attributeinformation such as formats, and pair information of the logical volumesare defined. Here, for convenience of explanation, logical volumenumbers are treated as unique to respective logical volumes in a datacenter.

Note that it is also possible to set the logical volume numbers so as tobe uniquely defined by a unit of each storage system and specified inconjunction with identifiers of the storage systems. “Not used” in avolume state indicates that a logical volume is set but is not used yet.“Primary” indicates that a logical volume is in a state in which thelogical volume can operate normally as the primary volume of the pairvolume described above. “Normal” indicates that a logical volume is notset as a pair with another logical volume but is in a normal state.“Secondary” indicates that a logical volume is a secondary volume andcan operate normally. Volume state information indicating a state of apair will be described later.

This example shown in FIG. 3 represents states of logical volumes in adata center system of this application. A logical volume number 1indicates the logical volume 110 (ORG1) of the first storage system 10,and a logical volume number 2 indicates a state in which the logicalvolume 150 (Data 1) of the second storage system 15 and the pair number1 form a pair. Similarly, a logical volume 151 (JNL1) of the secondstorage system 15 is represented as a logical volume number 3. A logicalvolume 201 of the third storage system 20 is represented as a logicalvolume number 4, and a logical volume 200 of the third storage system 20is represented as a logical volume number 5. Note that, although notused, the logical volume 120 (ORG2) is defined as a logical volumenumber 6.

A column of a physical address in FIG. 3 indicates addresses on theactual HDDs 100. On the basis of this information, microprocessors (notshown) on disk adapters 80 in FIG. 2 controls an operation for recordingdata on the actual HDDs 100 from the caches 60 and an operation forreading out data from the HDDs 100 to the caches 60.

The storage system 10 is described above as a representative storagesystem. However, the other storage systems 15 and 20 shown in FIG. 1also have substantially the same structure. The connection unit 55 maybe constituted by a switch or the like for directly connecting channeladapters and caches or the like or may adopt a connection system using abus. Note that FIG. 2 shows a state in which there are the sharedmemories 70 in the caches 60. However, the shared memories 70 may beconnected to the connection unit 55 separately from the caches 60.

Next, an operation for reflecting data update, which is applied to theprimary logical volume 110 (ORG1) in the storage system 10 in the firstsite, on the logical volume 200 (Data2) of the storage system 20 in thethird site via the storage system 15 in the second site (intermediatesite) will be explained with reference to FIG. 1.

Here, first, journal data will be explained. In order to facilitateexplanation, a logical volume of an update source, in which data isupdated, is distinguished from the other logical volumes to be referredto as a source logical volume, and a volume, which retains a copy of theupdate source logical volume, is referred to as a copy logical volume.

The journal data consists of, when data update is applied to a certainsource logical volume, at least updated data itself and updateinformation indicating to which position of the source logical volumethe update is applied (e.g., a logical address on the source logicalvolume).

In other words, as long as the journal data is retained when data in thesource logical volume is updated, the source logical volume can bereproduced from the journal data.

On the premise that there is a copy logical volume having the same dataimage as the source logical volume at a certain point in time, as longas the journal data is retained every time data in the source logicalvolume after that point is updated, it is possible to reproduce the dataimage of the source logical volume at or after the certain point in timein the copy logical volume.

If the journal data is used, the data image of the source logical volumecan be reproduced in the copy logical volume without requiring the samecapacity as the source logical volume. A volume in which the journaldata is retained will be hereinafter referred to as a journal logicalvolume.

Data update will be further explained with reference to FIG. 4. FIG. 4shows a state in which data from addresses 700 to 1000 of a certainsource logical volume is updated (updated data 630). In this case, in ajournal logical volume forming a pair with the source logical volume,data itself updated as the journal data 950 is recorded in a write dataarea 9100 as write data 610, and information relating to update, forexample, information indicating which position is updated is recorded asupdate information 620 in an update information area 9000.

The journal logical volume is used in a state in which it is dividedinto a storage area 9000 (update information area), in which the updateinformation 620 is stored, and a storage area 9100 (write data area), inwhich write data is stored. Update information is stored in the updateinformation area 9000 in an order of update (an order of an updatenumber) from the top of the update information area 9000. When theupdate information reaches the end of the update information area 9000,the update information is stored from the top of the update informationarea 9000. Write data is stored in the write data area 9100 from the topof the write data area 9100. When the write data reaches the write dataarea 9100, the write data is stored from the top of the write data area9100. It is needless to mention that it is necessary to apply updatework to a logical volume of a copy destination on the basis ofinformation in the journal logical volume before the data exceeds acapacity reserved for the journal logical volume. A ratio of the updateinformation area 9000 and the write data area 9100 may be a fixed valueor may be set by the maintenance terminal or the host computer 5.

In FIG. 1, when the storage system 10 receives a write instruction forthe data in the primary logical volume 10 (ORG1) in the storage system10 from the host computer 5 (arrow 250 shown in FIG. 1), the data in theprimary logical volume 110 (ORG1) in the first storage system 10 isupdated. Then, the logical volume 150 (Data1) in the storage system 15in the second site (intermediate site), which forms a pair with theupdated primary logical volume 110 (ORG1), is updated in the same manner(update of a synchronized pair). Consequently, the second storage system15 can take over the job immediately even if a failure has occurred inthe first storage system 10. This is because the second storage system15 retains the secondary logical volume 150 (Data1) having the same dataimage as the primary logical volume 110 (ORG1) used by the host computer5.

On the other hand, when data update is applied to the logical volume 150(Data1), the storage system 15 in the second site saves journal data inthe logical volume 151 (JNL1) (hereinafter referred to as a journalvolume according to circumstances) (arrow 260 shown in FIG. 1).

The journal data, which is accumulated in the logical volume 151 (JNL1)for accumulation of journal data in the second storage system 15, isasynchronously transferred to the logical volume 201 (JNL2) for journalaccumulation in the third storage system 20 located a long distanceapart from the second storage system 15 via the connection line 240(arrow 270 shown in FIG. 1) (hereinafter referred to as a PUSH system).The third storage system 20 reproduces the logical volume 200 (Data2)corresponding to the logical volume 150 in the second storage system 15using the journal data in the journal volume 201 (JNL2) in the storagesystem 20 (arrow 280 shown in FIG. 1, restore processing).

The data in the journal volume in the second storage system 15 may beread out from the third storage system 20 and accumulated in the logicalvolume 201 (JNL2) in the storage system 20 (hereinafter referred to asPULL system).

This PULL system will be explained specifically. Upon receiving aninstruction to read journal data (hereinafter referred to as journalread instruction) from the third storage system 20, the second storagesystem 15 reads out journal data from the journal logical volume 151(JNL1) and sends the journal data to the third storage system 20.

Thereafter, the third storage system 20 reads out the journal data fromthe journal logical volume (JNL2) 201 according to restore processing350 to be described later and updates the data in the logical volume 200(Data2). This completes the processing for reflecting the data update,which is carried out for the primary logical volume 110 (ORG1) in thestorage system 10 in the first site, on the secondary logical volume 200(Data2) in the storage system 20 in the third site.

By saving the journal data in the journal volume 201, for example, it isalso possible not to perform data update for the secondary logicalvolume 200 (Data2) when the journal data is received, that is, not tocreate a copy of the primary logical volume 110 (ORG1) in the secondarylogical volume 200 (Data2) using the journal data (restore processing350) when a load of the storage system 20 is high, and update the datain the secondary logical volume 200 (Data2) after a short time when aload of the storage system 20 is low.

As described above, the logical volume 151 (JNL1) in the second storagesystem 15 shown in FIG. 1 is a storage area dedicated for journal dataand can be made smaller than a storage area that is a data copy object.This makes it possible to copy data to the second and the third storagesystems 15 and 20 from the first storage system 10 by controllingconsumption of a storage area in the second storage system 15.

Next, setting for an entire data center system will be explainedspecifically. This setting is adopted in performing an operation forreflecting the data update for the logical volume 110 (ORG1) in thestorage system 10 on the second storage system 15 in the intermediatesite and the third storage system 20 in the third site.

In order to establish a data center system consisting of plural sites asshown in FIG. 1, first, for example, setting for the logical volume 150(Data1) and the journal volume 151 (JNL1) to form a journal group isrequired. The journal group means a pair of logical volumes. Asexplained above, the journal group consists of a logical volume and ajournal volume in which, when an instruction to write data in thelogical volume is received, the write instruction is sectioned intoupdate information such as a write destination address and write dataand accumulated.

In the example of FIG. 1, the logical volume 150 (Data1) and the logicalvolume 151 (JNL1) form a journal group in the storage system 15, and thelogical volume 201 (JNL2) and the logical volume 200 (Data2) form ajournal group in the storage system 20.

A flowchart in FIG. 5 shows an initial setting procedure of the datacenter system of the present invention. A user sets journal groups forthe respective storage systems using GUIs (graphical user interfaces)included in the host computers 5, 6 and 7 or the maintenance terminalsnot shown in FIG. 1 (steps 900 and 905).

In FIG. 1, the journal groups in the storage system 15 and the storagesystem 20 in the second and the third sites, that is, the pair of Data1and JNL1 and the pair of Data2 and JNL2 are referred to as a journalgroup 1 and a journal group 2, respectively. The journal groups may bereferred to as journal pairs. More specifically, the journal groups areretained in the shared memories 70 as a journal group settinginformation table 550.

Moreover, the user designates information indicating a data copy objectand information indicating a data copy destination and sends a pairregistration instruction to the first and the second storage systems 10and 15 using the maintenance terminals or the host computers 5 and 6connected to the respective storage systems (step 910). Morespecifically, the user sets a pair relation between the logical volume110 (ORG1) and the logical volume 150 (Data1) in FIG. 1.

When the logical volume 110 (ORG1) and the logical volume 150 (Data1)are set as a pair, according to a status of the pair, write processingapplied to a primary logical volume serves as an opportunity forperforming various kinds of processing with respect to a secondarylogical volume. For example, the status of the pair includes a suspendstate, a pair state, an initial copy state, and the like. When thestatus of the pair is the pair state, processing for writing data, whichis written in the primary logical volume, in the secondary logicalvolume as well is performed. When the status of the pair is the suspendstate, data, which is written in the primary logical volume, is notreflected on the secondary logical volume, and a difference between theprimary logical volume and the secondary logical volume is retained inthe first storage system 10 using a bit map.

As described above, setting information for the journal group andsetting information for this pair are accumulated in the shared memories(SMs) 70 shown in FIG. 2. The microprocessors on the channel adapters 50execute processing on the basis of the information. It is needless tomention that, in this processing, the shared memories (SMs) 70 do notnecessarily have to be referred to every time the processing isperformed, and information necessary for processing for a channelprocessor may be transferred onto a local memory of the channelprocessor in advance.

FIG. 6 shows an example of a pair setting information table 500 showingstates of pairs. A first row of FIG. 6 indicates that a pair of thelogical volume 110 (ORG1) (logical volume number 1) in the first storagesystem 10 and the logical volume 150 (Data1) (logical volume number 2)in the second storage system 15 is generated as a pair number 1. In step910 in FIG. 5, initial copy, which is initialization processing formaking data images of the logical volume 110 (ORG1) and the logicalvolume 150 (Data1) identical, is further performed.

In the next step 915, the user designates the logical volume 150 (Data1)and the logical volume 200 (Data2) to form a pair and performs initialcopy. This is for giving the identical data image to the logical volume150 (Data1) and the logical volume 200 (Data2) as in the processing instep 910.

A row of a pair number 2 in FIG. 6 shows a state in which this pair isset. This pair is deleted after the initial copy processing ends (step920).

When the data image of the logical volume 110 (ORG1) in the firststorage system is copied to the logical volumes 150 (Data1) and 200(Data2) in the storage systems 15 and 20, copy programs in the storagesystems 15 and 20 inform the maintenance terminal or the host computer 5of the end of the copy. After this initialization processing, accuraterestore processing (recovery) for data in the storage system 20 becomespossible.

Next, an operation of the storage system in an embodiment of the storagesystem of the present invention will be explained in detail withreference to FIGS. 8 and 9.

FIG. 8 is a block diagram showing data write processing that isperformed by the storage system 15 in the second site. The secondstorage system 15 is connected to the storage system 10 in the firstsite by the connection line 200 via the channel adapter 50. The firststorage system 10 is connected to the host computer 5 via the connectionline 210.

First, the first storage system 10 receives a data write instructionfrom the host computer 5 via the connection line 210 (arrow 250 in FIG.8). When the data is written in the logical volume 110 (ORG1), thesecond storage system 15 receives the data write instruction from thefirst storage system 10 via the connection line 220.

An arrow 1100 shown in FIG. 8 indicates a flow of data in the case inwhich the data write instruction for writing data in the logical volume150 (Data1) of a data copy destination in the storage system 15 in thesecond site is received.

Upon receiving the data write instruction for writing data in thelogical volume 150 (Data1) from the first storage system, the channeladapter 50 retains the write data and update information in the cachememory 60. The write data on the cache 60 is written in the logicalvolume 150 (Data1) by the disk adapter 80 at timing different fromtiming for writing data in the cache 60 (arrow 1110 in FIG. 8).

Similarly, the update information (including at least an updatedaddress) recorded on the cache 60 is written in an update informationarea of the logical volume 151 (JNL1), and the write data is furtheraccumulated in a write data area of the logical volume 151 (JNL1) (arrow1120 in FIG. 8). The disk adapter 80 writes the write data and theupdate information on the cache 60 in an address allocated to thelogical volume 151 (JNL1) on the HDD (arrows 1130 and 1140 in FIG. 8).

On the other hand, a channel adapter 51, which is connected to the thirdstorage system 20 via the connection line 240, receives a readinstruction for the logical volume 151 (JNL1) from the storage system20. This point will be described later with reference to FIG. 11. Notethat the channel adapters 50 and 51 are channel adapters of the samestructure but are given different numbers according to circumstances forconvenience of explanation.

FIG. 9 is a flowchart showing processing in the case in which thelogical volume 150 (Data1) in the storage system 15 in the second sitereceives an instruction from the storage system 10 in the first site.

Upon receiving an access instruction from the first storage system 10,the microprocessor mounted on the channel adapter 50 in FIG. 8(hereinafter simply referred to as channel adapter 50) checks a type ofthe instruction (step 1210 in FIG. 9). This is because a channel adaptermay receive a write instruction as in the channel adapter 50 in FIG. 8or may receive a read instruction from another storage as in the channeladapter 51.

If the received access instruction is not a write instruction but ajournal read instruction from the third storage system 20, the channeladapter 50 performs journal read reception processing to be describedlater (steps 1215 and 1220).

If the access instruction is a write instruction in step 1210, thechannel adapter 50 checks a volume state of the logical volume 150(Data1) (step 1240).

As shown in FIG. 3, states of the respective logical volumes areaccumulated in the shared memories (SMs) 70 as volume information in atable format as described above.

If the volume state of the logical volume 150 (Data1) is not normal instep 1240, since access to the logical volume 150 (Data1) is impossible,the channel adapter 50 informs the host computer 5 of abnormality andends the processing (step 1230).

If the volume state of the logical volume 150 (Data1) is normal in step1240, the channel adapter 50 reserves the cache memory 60 and receivesdata (step 1250). More specifically, the channel adapter 50 informs thefirst storage system 10 that the channel adapter 50 is prepared forreceiving data. Thereafter, the first storage system 10 sends write datato the second storage system 15. The channel adapter 50 in the secondstorage system 15 receives the write data and saves the write data inthe prepared cache memory 60 (step 1250, arrow 1100 in FIG. 8).Thereafter, in step 1260, the channel adapter 50 informs the firststorage system 10 of the end of the processing.

Next, the channel adapter 50 checks whether the logical volume 150(Data1) is a logical volume having a journal group with reference to thejournal group setting information table 550 (see FIG. 7) recorded in theshared memories (SMs) 70 (step 1270).

Here, FIG. 7 will be explained in detail. FIG. 7 is a diagram showinghow journal pairs are formed among logical volumes. A first rowindicates that logical volumes with logical volume numbers 2 and 3 forma journal group. More specifically, the first row indicates that thelogical volume 150 (Data1) and the logical volume 151 (JNL1) in thestorage system 15 form a journal pair.

If the logical volume 150 (Data1) is a logical volume having a journalgroup, the channel adapter 50 applies, journal creation processing tothis volume and the journal logical volume 151 (JNL1) forming thejournal group (step 1265). Thereafter, at arbitrary timing, the diskadapter 80 writes data in the logical volume 150 (Data1) and the logicalvolume 151 (JNL1) that are defined on the HDD (step 1280, arrows 1130and 1140 in FIG. 8).

As described above, the journal is created in the second storage system15, the journal data is sequentially stored in the journal volume 151(JNL1). The journal data is sent to the journal volume 201 (JNL2) in thethird storage system 20 with a fixed factor as an opportunity. Onemethod for sending the journal data is the PUSH system described above,and there is the PULL system as another method. The PULL system will beexplained with reference to FIG. 10.

FIG. 10 is a block diagram showing an operation (journal readinstruction reception processing) of the channel adapter 51 in thesecond storage system 15 that has received a journal read instruction.FIG. 11 is a flowchart of the operation. An operation in the case inwhich the second storage system 15 has received the journal readinstruction from the third storage system 20 will be explained withreference to FIGS. 10 and 11.

The channel adapter 51 in the second storage system 15 receives anaccess instruction from the third storage system 20 (arrow 1410 in FIG.10). When the access instruction is a journal read instruction, thechannel adapter 51 checks whether a journal group state is “normal” withreference to FIG. 7 (step 1510). If the journal group state is a stateother than “normal”, for example, “failure”, the channel adapter 51informs the third storage system 20 of the journal group state and endsthe processing. The third storage system 20 performs processingaccording to the informed journal group state. For example, if thejournal group state is “failure”, the channel adapter 51 ends thejournal read processing (step 1515).

If the journal group state is “normal” in step 1510, the channel adapter51 checks a state of a journal logical volume (step 1520).

If the volume state of the journal logical volume is not “normal”, forexample, if the volume estate of the journal logical volume is “failure”in step 1520, the channel adapter 51 changes the journal group stateshown in FIG. 7 to “failure”, informs the storage system 20 of thejournal group state, and ends the processing (step 1525).

In step 1530, the channel adapter 51 checks whether journal data, whichhas not been sent, is present. If journal data, which has not been sent,is present, the channel adapter 51 sends the journal data to the thirdstorage system 20 (step 1550). If all journal data have been sent to thestorage system 20, the channel adapter 51 informs the third storagesystem 20 of “absence of journal data” (step 1560). Thereafter, thechannel adapter 51 opens an area in which the journal data was present(step 1570).

Processing in the case in which journal data, which has not been sent,is present will be explained more in detail with reference to FIG. 10.If journal data, which has not been sent, is present, the channeladapter 51 reserves the cache memory 60 and instructs the disk adapter81 to read the update information and the write data in the cache memory60 (arrow 1440 in FIG. 10).

In read write processing of the disk adapter 81, the disk adapter 81reads the update information and the write data from the logical volume151 (JNL1) that is a logical area formed in a distributed manner on theHDD 100, saves the update information and the write data in the cachememory 60, and informs the channel adapter 51 of the same (arrows 1430and 1450 in FIG. 10).

The channel adapter 51 is informed that the reading of the write dataand the update information in the cache memory 60 has ended, sends theupdate information and the write data from the cache memory 60 to thethird storage system 20, and then opens the cache memory 60 that retainsjournal data (arrow 1460 in FIG. 10).

The channel adapter 51 opens the storage area for the journal data thatwas sent to the third storage system 20 at the time of the processing ofthe last journal read instruction (step 1570).

Note that, in the journal read reception processing described above, thesecond storage system 15 sends the journal data to the third storagesystem 20 one by one. However, the second storage system 15 may sendsplural journal data to the storage system 20 simultaneously.

The number of journal data to be sent at one journal read instructionmay be designated in a journal read instruction by the third storagesystem 20 or may be designated in the second storage system 15 or thethird storage system 20 by a user, for example, when a journal group isregistered.

Moreover, the number of journal data, which is sent at one journal readinstruction, may be changed dynamically according to transfer ability,load, or the like of the connection line 240 for the second storagesystem 15 and the third storage system 20. In addition, a transferamount of journal data may be designated taking into account a size ofwrite data of journal data rather than the number of journal data.

In the journal read instruction reception processing described above,journal data is read in the cache memory 60 from the HDD 100. However,when journal data is present in the cache memory 60, the processing isunnecessary.

The processing for opening a storage area for journal data in thejournal read instruction reception processing is performed at the timeof processing for the next journal read instruction. However, thestorage area may be opened immediately after sending journal data to thethird storage system 20. In addition, it is also possible that the thirdstorage system 20 sets an update number, which may be opened, in ajournal read instruction, and the second storage system 15 opens astorage area for journal data in accordance with an instruction of thethird storage system 20.

The third storage system 20 having received the journal data stores thereceived journal data in the journal volume 201 (JNL2). Thereafter, thestorage system 20 performs journal restore.

The third storage system 20 executes a journal restore program torestore data in the logical volume 200 (Data2) from the journal volume201 (JNL2). Note that an area, in which the restored journal data wasstored, is purged (opened) and used for storage of new journal data.

Next, this journal restore processing will be explained in detail. FIG.12 is a block diagram showing the restore processing, and FIG. 13 is aflowchart of the restore processing.

An operation in which a channel adapter 53 in the third storage system20 updates data using journal data will be explained with reference toFIGS. 12 and 13. A disk adapter 83 in the storage system 20 may performthe restore processing.

In step 2010 in FIG. 13, the channel adapter 53 checks whether restoreobject journal data is present in the logical volume 201 (JNL2). If thejournal data is not present in the logical volume 201 (JNL2), thechannel adapter 53 ends the restore processing once, and after a fixedtime, resumes the restore processing (step 2010).

If the restore object journal data is present in step 2010, the channeladapter 53 applies the following processing to oldest (smallest) journaldata. The channel adapter 53 only has to continuously give updatenumbers to the journal data and apply the restore processing to updateinformation of journal data having an oldest (smallest) update number.The channel adapter 53 reserves the cache memory 60 (arrow 1910 in FIG.12) and reads out update information and write data to the disk adapter83 from the update information with the oldest number (step 2020, arrows1920 and 1930 in FIG. 12).

More specifically, the disk adapter 83 in the third storage system 20reads update information form the HDD 10, in which the updateinformation is stored, according to read/write processing 340, saves theupdate information in the cache memory 60, and informs the channeladapter 53 of the update information.

Similarly, the disk adapter 83 in the third storage system 20 acquireswrite data on the basis of the read update information (step 1930) andissues an instruction to read the write data in an area of the cachememory 60 corresponding to a part of the logical volume 200 (Data2) thatshould be updated (step 2020, arrow 1940 in FIG. 12).

Then, the disk adapter 83 writes the write data from the secondarylogical volume cache area into the secondary logical volume 200 (Data2)asynchronously to the restore processing (arrow 1950 in FIG. 12, step2030). Thereafter, the disk adapter 83 opens (purges) an area where theupdate information and the write information of the secondary logicalvolume (JNL2) reflected on the secondary logical volume 200 (Data2) werepresent (step 2040). The disk adapter 83 judges whether to perform therestore processing continuously (step 2050). If the restore processingis performed continuously, the disk adapter 83 returns to step 2010, andif not, ends the restore processing.

In the restore processing described above, journal data is read in thecache memory 60 from the HDD 100. However, when the journal data ispresent in the cache memory 60, the processing is unnecessary.

Second Embodiment

Next, a second embodiment of the present invention will be explained.FIG. 14 is a block diagram for explaining a concept of the secondembodiment. The second embodiment is different from the first embodimentin that the logical volume 150 (Data1) of the second storage system is avolume, which is virtually set, and does not have a storage area foractually accumulating data. FIG. 15 is a flowchart showing an initialsetting procedure. FIG. 16 is a diagram showing a pair information tablefor realizing the second embodiment. FIG. 17 is a block diagram showinga flow of data in access instruction reception processing in thisembodiment. FIG. 18 is a flowchart showing processing of the secondstorage system 15 in the second embodiment. The second embodiment willbe hereinafter explained with reference to FIGS. 15, 16, 17, and 18.

First, the flowchart shown in FIG. 15 shows the initial settingprocedure in the second embodiment. A user sets a journal group for thethird storage system 20 using GUIs (graphical user interfaces) includedin the host computers 5, 6, and 7 or maintenance terminals not shown inFIG. 14 (step 3000). More specifically, the user writes the logicalvolume 200 (Data2) and the logical volume 201 (JNL2) in the journalgroup setting information table as shown in FIG. 7.

Next, the user designates information indicating a data copy object andinformation indicating a data copy destination and performs pair settingusing the maintenance terminals or the host computers 5, 6, and 7connected to the respective storage system (step 3100). Morespecifically, the user sets a pair relation between the logical volume110 (ORG1) and the logical volume 200 (Data2) in FIG. 14.

In this step 3100, the user designates the logical volume 110 (ORG1) andthe logical volume 200 (Data2) to form a pair and performs initial copy.This is for giving an identical image data to the logical volume 110(ORG1) and the logical volume 200 (Data2). Then, the pair is deletedafter the initial copy processing ends (step 3200).

Next, the user sets a pair relation between the logical volume 110(ORG1) and the logical volume 150 (Data1) in the first storage system 10and the second storage system 15 (step 3300).

FIG. 16 shows a pair information table 510 in the second embodiment. Astructure of the pair information table 510 is substantially the same asthat shown in FIG. 6 but is different in that data indicating whether apair is virtualized is retained for each pair. In a pair indicated by apair number 1 in FIG. 16, a column of virtualization is ON. Thisindicates that a secondary logical volume of the pair is virtualized.

The user registers the logical volume 150 (Data1) and the logical volume151 (JNL1) as a journal group (step 3400).

The above is the procedure for the initial setting in the secondembodiment. After this initialization processing, accurate restoreprocessing (recovery) for data in the storage system 20 becomespossible.

Next, FIG. 17 will be explained. Upon receiving a write command for datafrom the host computer 5, the first storage system 10 shown in FIG. 17writes the data in the designated logical volume 110 (ORG1) (arrow 250shown in FIG. 17). When the data is written in the logical volume 110(ORG1), if there is a logical volume of the other storage system (inthis embodiment, the logical volume (Data1) of the second storage system15) forming a pair with this logical volume 110 (ORG1), the firststorage system 10 issues the write command for the data, which is thesame as the write command received from the host computer 5, to thesecond storage system. This write command is received by a channeladapter 54 in the second storage system, and instruction receptionprocessing 310 is performed by a processor on the channel adapter 54.

In the first embodiment, that is, when the logical volume 150 (Data1) inthe second storage system 15 has an entity, in this instructionreception processing 310, the processor analyzes the write command,stores write data in an area on a cache memory corresponding to a writedestination of a designated logical volume, and accumulates updateinformation on a cache memory corresponding to an area where the journalvolume 151 (JNL1), in which the update information is written, iswritten. The disk adapter 80 performs processing for writing data on thecache memory in a logical volume area corresponding thereto according tocircumstances.

On the other hand, in the second embodiment, first, the second storagesystem 15 judges whether the logical volume 150 (Data1) in the secondstorage system 15 designated as a write destination is a logical volume,which should be treated as one having an entity, with reference to thepair information table 510 shown in FIG. 16. The second storage system15 recognizes that the logical volume (Data1) 150 in the second storagesystem 15 (itself) is a virtualized logical volume. Since the secondstorage system 15 treats this logical volume (Data1) 150 as one nothaving an entity, the second storage system 15 accumulates write data ina cache area corresponding to the write data area of the logical volume(JNL1) 151, and accumulates information concerning to which area of thelogical volume (Data1) 150 the write instruction is applied as updateinformation in a cache area corresponding to the update information areaof the logical volume (JNL1) 151 (arrows 1111 and 1120 shown in FIG.17). The disk adapter 80 writes data on the HDD 100 in which a logicalvolume corresponding to the data on the cache memory is defined (arrows1130 and 1140 in FIG. 17).

The access instruction reception processing will be further explainedwith reference to FIG. 18. Upon receiving an access instruction, first,the channel adapter 54 in the second storage system 15 confirms whetherthe instruction is a write instruction (step 9210). If the instructionis not a write instruction, for example, if the instruction is aninstruction such as a journal read instruction, the channel adapter 54performs processing of the instruction (steps 9215 and 9220).

Next, the channel adapter 54 judges whether a volume, for which thewrite instruction has been received, is a normal volume (step 9240). Ifthe volume state is not normal, the channel adapter 54 informsabnormality to a host apparatus, which has issued the instruction, viathe maintenance terminal and ends the processing (step 9230). Next, thechannel adapter 54 judges whether the logical volume, which is a writedestination, is a virtual volume using the pair information tale 510 inFIG. 16 (step 9250). If the logical volume is a virtual volume, thechannel adapter 54 performs journal creation processing (step 9265) and,after completing the processing, informs the host apparatus (firststorage system) of the end of the processing (step 9275).

If the logical volume is not a virtual volume, the channel adapter 54receives data in a cache area corresponding to the logical volume (step9260) and informs the host apparatus of the end of the data reception(step 9270). Next, the channel adapter 54 judges whether the logicalvolume is a logical volume having a journal group (step 9280). If thelogical volume is a logical volume having a journal group, the channeladapter 54 performs journal creation processing (step 9265).

In this way, since the pair information table 510 also includesvirtualization information indicating whether a secondary logical volumeis virtualized, actual writing of data in the secondary logical volumecan be controlled. This makes it possible to define the secondarylogical volume as a destination of remote copy without giving asubstantial storage capacity to the secondary logical volume.

Third Embodiment

Next, a third embodiment of the present invention will be explained. Inthe third embodiment, a constitution for making this virtualizedsecondary logical volume available for other applications will beexplained.

FIG. 19 is a diagram showing the third embodiment conceptually.Differences from the second embodiment shown in FIG. 14 will beexplained in detail. In FIG. 19, for convenience of explanation, achannel adapter 56 for receiving a write instruction for data, a channeladapter 57 connected to the host computer 6 via a connection line 255,and a channel adapter 58 connected to the third storage system 20 areclearly shown with the first storage system 10 as a host apparatus. Itis needless to mention that channel adapters are also present in FIGS. 1and 14. The logical volume (Data1) 110 in the first storage system formsa remote copy pair with the logical volume 150 (Data1) in the secondstorage system 15, and as in the second embodiment, the logical volume150 (Data1) is virtualized. Copying of data from this logical volume 150(Data1) to the logical volume 200 (Data2) in the third storage system isas explained in the second embodiment.

In the third embodiment, the logical volume 150 (Data1) is furtherconnected to the host computer 6 via the channel adapter 57. Then, thethird embodiment is particularly characterized by making it possible towrite data from the host computer 6 to the logical volume 150 (Data1).

Next, it will be explained how configuration information on the sharedmemory 70 for making it possible to use the logical volume 150 (Data1)in the host computer 6 is held. The configuration information includes,in addition to the above-mentioned tables (FIGS. 3, 7, and 16), achannel adapter connection information table 5000 that indicates aconnection relation among channel adapters and host apparatuses.

Upon receiving an access request (read/write request for data) from ahost apparatus, a processor on each of the respective channel adaptersin the second storage system 15 judges a host apparatus or anotherchannel adapter, which is connected to the channel adapter, withreference to the connection information table 5000 in FIG. 20. Whenanother storage system or a channel adapter of another storage system isset as the host apparatus, the channel adapter in the second storagesystem 15 judges that remote copy will be performed, and judges whethera logical volume set as a write destination of the remote copy isvirtualized in accordance with the procedure explained in the secondembodiment. If the logical volume set as a write object is notvirtualized, the channel adapter performs write processing. On the otherhand, if the logical volume is virtualized, the channel adapter performsonly writing in a journal volume as explained in the second embodiment.

If it is judged that the host apparatus connected to the channel adapteris not another storage system (or a channel adapter in the storagesystem), the channel adapter executes write processing for writing datain the logical volume set as a write object. The channel adapterperforms this processing by writing data in a cache area correspondingto the logical volume set as the write object and writes the data in alogical volume, for which a disk adapter is defined on the HDD 100,asynchronously to the writing in the cache area. In this way, thestorage system judges whether data, for which I/O (access request) isreceived, may be written in a designated logical volume.

Since the storage system can only judge whether a logical volume isvirtualized, the storage system cannot judge whether the data may beactually written in the volume. Thus, the storage system identifies datafrom a host apparatus that may actually be written according to whichadapter receives the data. Consequently, the storage system can use alogical volume that is virtualized by another host apparatus.

Note that, as another method, when an identifier indicating remote copydata is present in a data set transferred in remote copy, writing ofdata in a virtualized volume may be restricted only in the case ofremote copy using the identifier.

In the present invention, a case in which it is effective to virtualizea volume is explained with remote copy as an example. However, it isalso possible to virtualize a logical volume set as an object of afunction other than the remote copy, for example, an E-COPY command,which is a standard command of SCSI.

Note that it is needless to mention that, in FIG. 14, the instructionreception processing and the read/write processing 320 are performed inthe channel adapters 56, 57, and 58. In addition, it is also possible toallocate this processing to other processors.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be explained.FIG. 21 shows an example of a setting screen for remote copy pairgeneration that is displayed on the host computer 5 or the maintenanceterminal. In the example of FIG. 21, a user has set Vol #1 and Vol #2 asa pair in a pair volume designation display section 4100 in an area4600, in which setting for pair generation is performed, on a screen4000. In performing the setting for pair generation, the user can choosewhether to virtualize Vol #2, which corresponds to a secondary logicalvolume, in a virtual Vol designation display section 4300 in the area4600 in which setting for pair generation is performed. In the exampleof FIG. 21, the user has chosen to virtualize the Vol #2 correspondingto a secondary logical volume.

There is a connection setting section 4400 in an area 4700 thatindicates to which storage system or host apparatus each channel adapterin each storage system is connected. This connection setting unit 4400makes it possible to set a connection relation between each channeladapter and storage system. Note that a connection destination of thechannel adapter may be a channel adapter of another storage system orhost apparatus.

An example of a screen of the connection setting section 4400 indicatesthat the channel adapters 56, 57, and 58 are connected to the firststorage system 10, the host computer 5, and the third storage system 20,respectively.

Moreover, as shown in FIG. 21, there is a logical volume use settingsection 4500 in an area 4800 showing volumes used by host apparatuses.This logical volume use setting section 4500 makes it possible to set alogical volume that is used by each host computer. In an example of ascreen of the logical volume use setting section 4500, the logicalvolume 150 is set as being used by the host computer 6. It should benoted here that, since the logical volume 150 is already used by thehost computer 6, if the logical volume 150 is designated as the Vol #2in the pair volume designation display section 4100, a pair cannot bedesignated unless virtualization is set for the logical volume 150.

As described above, the user chooses not to virtualize the logicalvolume 150 (Data1) in the second storage system 15 when the userattaches importance to safety and failure resistance property, andchooses to virtualize the logical volume 15 (Data1) when the user wishesto utilize a volume capacity in the second storage system 15 as much aspossible. This makes it possible to establish a system according to apurpose and cost. Note that a procedure for copying data from the firststorage system 10 to the third storage system 20 after virtualizing thesame is as explained in the second embodiment.

Fifth Embodiment

Next, as a fifth embodiment of the present invention, a case will beexplained in which, when a failure has occurred in the first storagesystem 10, a job is continued in the third storage system 20 located along distance apart from the first storage system 10 (failover).

As shown in FIG. 22, the first storage system 10, the host computer 5,the third storage system 20 located a long distance apart from the firststorage system 10, the second storage system 15 interposed between thefirst storage system 10 and the host computer 5, the host computer 6,and the host computer 7 connected to the third storage system 20 areconnected by connection lines. In the event that some failure hasoccurred in the first storage system, in taking over a job of the firststorage system 10 in the third storage system 20 located a long distanceapart from the first storage system 10, it is a problem in that thelogical volume 110 (ORG1) retained by the first storage system 10 andthe logical volume 200 (Data2) retained by the third storage system 20are not the same data. Since the first storage system 10 and the secondstorage system 15 are synchronous but the second storage system 15 andthe third storage system 20 are asynchronous, a copy of copy object datain the first storage system 10 is not completely created in the thirdstorage system 20 (data, which has not reached, is not reflected on thelogical volume 200 (Data2).

Thus, in order to resume the job in the third storage system 20, first,the data, which has not reached, is reflected on the logical volume 200(Data2). In the second and third embodiments and the fourth embodimentin which a user has chosen to virtualize a logical volume, the secondstorage system 15 does not include the logical volume 150 (Data1), butjournal data is present in the journal volume 151 (JNL1). Thus, thejournal data is sent to the third storage system 20 to reflect the data,which has not reached, on the logical volume 200 (Data2) according tothe restore processing 350 shown in FIG. 22. Consequently, a completecopy of the copy object data can be created in the logical volume 200(Data2) in the third storage system 20. Thereafter, the third storagesystem 20 can receive an instruction from the host computer 7.

As a result, resistance against a failure can be kept while virtualizingthe logical volume 150 (Data1) in the second storage system to reduce avolume capacity.

Sixth Embodiment

In addition, as a sixth embodiment, as shown in FIG. 23, if it isdesired to continue a jog in the second storage system 15, since thelogical volume 150 (Data1) in the second storage system 15 isvirtualized, it is necessary to assign a logical volume to the secondstorage system 15 anew. After assigning the logical volume to the secondstorage system 15, journal data is acquired from the third storagesystem 20 according to the journal read processing 330 to perform therestore processing 350 in the second storage system 15.

Consequently, a copy of a copy source logical volume in the firststorage system 10 can be created in the logical volume assigned to thesecond storage system 15 anew. Thereafter, the second storage system 15can receive an instruction from the host computer 6.

The present invention has been explained specifically on the basis ofthe embodiments. However, it is needless to mention that the presentinvention is not limited by the embodiments, and various modificationsare possible within a range not departing from the scope of the presentinvention.

1. A remote copy system comprising: a first storage system coupled to an information processing apparatus, the first storage system including a first storage area in which the data from the information processing apparatus is written; and a second storage system coupled to the first storage system, the second storage system including a virtual volume defined by a logical address to be a write destination of data sent from the first storage system, the second storage system having a second storage area in which data for that logical address and update information concerning the data are written, and wherein data from the first storage system to be written in the logical volume of the second storage system, is written in the second storage area together with the update information of the data, instead of being written to an area indicated by the logical address.
 2. A remote copy system according to claim 1 wherein the second storage area has a smaller storage capacity than the first storage area.
 3. A remote copy system comprising: a first storage system having a first storage control unit for controlling data writing in a first logical volume with reference to a first shared memory; and a second storage system having a second storage control unit for controlling data writing in a second logical volume with reference to a second shared memory, wherein the remote copy system stores pair information defining a correspondence relationship between the first logical volume and the second logical volume, in the first shared memory, and information, which, when data is written in the second logical volume, defines a journal volume storing the data and update information of the data, in the second shared memory; when first data is written in the first logical volume, the first storage system issues a write instruction for the first data to the second storage control unit with the second logical volume as an object of writing on the basis of the pair information in the first shared memory, and when a write instruction to write data in the second logical volume is received from the first storage system, with reference to the second shared memory, the second storage system does not write the first data in the second logical volume, but instead writes the first data and update information of the first data in the journal volume if an area defined as the second logical volume is defined as a logical volume area other than the second logical volume, and writes the first data in the second logical volume if the area defined as the second logical volume is not defined as a logical volume other than the second logical volume.
 4. A storage system comprising: plural storage devices; and a storage control unit that receives a write instruction for data from an information processing apparatus and controls writing of the data in the storage devices; wherein the storage system has a shared memory that stores information for defining logical volumes on the storage devices as configuration information, and an area on the storage device in a first logical volume defined by the shared memory and an area on the storage device in a second logical volume defined by the shared memory are defined such that at least parts of the areas have overlapping addresses.
 5. A remote copy system comprising: a first storage system coupled to an information processing apparatus; and a second storage system coupled to the first storage system to receive data from the first storage system; wherein the first storage system has a first storage area in which the data sent from the information processing apparatus is written; the second storage system has a logical address for a write destination of the data sent from the first storage system, and also has a second storage area in which data and update information, which should be written to the logical address, and when a storage area is allocated to the logical address, the data is written in the storage area, and the data and the update information is written in a second storage area, and when a storage area is not allocated to the logical address, the data and the update information is written in the second storage area.
 6. The remote copy system according to claim 5, wherein the second storage area has a smaller capacity than the first storage area.
 7. A remote copy system comprising: a first storage system coupled to an information processing apparatus and sends and receives data to and from the information processing apparatus; a second storage system coupled to the first storage system and receives data from the first storage system; and a third storage system coupled to the second storage system and receives data from the second storage system; wherein the first storage system has a first storage area in which the data sent from the information processing apparatus is written, the second storage system has a logical address to be a write destination of the data sent from the first storage system, and also has a second storage area in which data, which should be written in the logical address, and update information concerning the data are written, and when a storage area is allocated to the logical address, the data is written in the storage area, and the data and the update information is written in a second storage area; when a storage area is not allocated to the logical address, the data and the update information is written in the second storage area; the third storage system has a third storage area in which the data read out from the second storage area in the second storage system and update information concerning the data are stored, and a fourth storage area that is a copy destination of the first storage area; and the data and the update information, which are stored in the second storage area, are read out from the third storage system and written in the third storage area after a predetermined time elapses, and thereafter the second storage area can be opened and is used for new storage.
 8. A remote copy system according to claim 7 wherein each of the second and the third storage areas have a smaller storage capacity than either of the first and the fourth storage areas.
 9. A remote copy system comprising: a first storage system coupled to a first information processing apparatus to send data to and receive data from the first information processing apparatus; a second storage system coupled to a second information processing apparatus and coupled to the first storage system to send data to and receive data from the second information processing apparatus, and to receive data from the first storage system; and a third storage system coupled to the second storage system to receive data from the second storage system; wherein the first storage system includes a first storage area in which the data sent from the information processing apparatus is written; the second storage system includes a logical address as a write destination of data sent from the first storage system, and includes a second storage area in which data targeted for the logical address, and update information concerning the data, are written; the third storage system includes a third storage area in which data received from the second storage area in the second storage system and update information concerning that data are stored, and includes a fourth storage area that is a copy destination of the first storage area; and data sent from the first storage system so as to be written to the logical address in the second storage system, is written in the second storage area together with update information, and a storage area for sending and receiving data to and from the second information processing apparatus is allocated to the logical address, and the data and the update information to be stored in the second storage area are read out from the third storage system and written in the third storage area, and thereafter the second storage area can be opened and used for additional storage.
 10. A remote copy system according to claim 9, wherein the second and the third storage areas are smaller than the first and the fourth storage areas. 